1. Field of the Invention
The present invention relates to pressure relief upon electric shut-off of a pump, and is particularly concerned with pressure relief within a predetermined time interval, for example within five second, upon shut-off of a spray gun.
2. Description of the Prior Art
Currently, particularly with respect to spray guns, manual pressure relief is required, as is warning of the danger of accidental injection of paint into the human body. Such warnings are contained in the owner's manuals for paint spray guns and current spray systems require the operator to follow specific instructions to avoid accidental injection. Prior designs for automatic pressure relief valves create additional problems and require additional cleaning and maintenance. Such valves are more prone to malfunction than a manual valve. A poorly-maintained automatic relief valve may become clogged and place the operator in jeopardy of injection because failure of a relief valve requires the user to clean the sprayer and spray tip with high pressure in the hose, pump unit and valve body. Automatic pressure relief systems have centered about the utilization of systems which require moving a piston or valve which comes in contact with the material being sprayed. The movement of the pressure relief mechanism is triggered by pressure sensing on the discharge side of the pump, electrical solenoid and time delay devices with pistons, valves or actuators that come into contact with the material being sprayed.